Thermal expansion studies on (CH3NH3)5Bi2Cl11 and (CH3NH3)5Bi2Br11 in the temperature range 80-350 K are reported. The dilatometric measurements revealed a considerable similarity with respect to the anisotropy of dilatations of both isomorphous crystals. A diffused thermal anomaly was found around 170 K in (CH3NH3)5Bi2Cl11 crystal.